1. Field of the Invention
The present invention relates to a method for controlling a parallel plate plasma processing apparatus that manufactures semiconductor devices and Micro Electro Mechanical System (MEMS) devices.
2. Description of the Related Art
For micro-fabrication of grooves in a space width of 10 nm and aspect of 15 or more on stacked films such as silicon, silicon oxidize, and silicon nitride, micro-fabrication is performed mainly using a parallel plate plasma processing apparatus that generates plasma in a region sandwiched between an upper electrode and a lower electrode. For the parallel plate plasma source, a capacitive coupling plasma (CCP) apparatus is used as well as a magnetic field VHF plasma apparatus is used including a supply for a VHF wave of 200 MHz and a magnetic field generating coil.
This magnetic field VHF plasma apparatus has a structure below. The upper electrode of the magnetic field VHF plasma apparatus includes a function of emitting VHF waves for plasma generation. For an upper electrode member, a dielectric ceramic material such as silica, yttria, and sapphire glass or a material that an aluminum material or stainless steel material is coated with a dielectric ceramic material is used for a surface contacting plasma, from viewpoints of contamination and foreign substances. Moreover, the plasma generation distribution and the in-plane distribution of the etching rate can be controlled using a magnetic field from a magnetic field generating coil. A radio frequency bias can be applied to the lower electrode on which a wafer is placed for anisotropy etching. See Japanese Patent Application Laid-Open Publication No. 2007-59567.
On the other hand, in the CCP etching apparatus, a plasma processing apparatus is disclosed for improving uniformity, which includes a circuit that adjusts electrical characteristics (impedance) on the counter electrode side on which a bias frequency is applied so as to prevent an electric current flowing into the counter electrode side from becoming the maximum. See Japanese Patent Application Laid-Open Publication No. 2011-82180, which discloses a control method in which a bias current is adjusted to a half of the maximum electric current or more.